If $x \star y = xy+2x-y$ and $x \triangleright y = x-3y$, find $(-1 \triangleright 2) \star 0$.
Answer: First, find $-1 \triangleright 2$ $ -1 \triangleright 2 = -1-(3)(2)$ $ \hphantom{-1 \triangleright 2} = -7$ Now, find $-7 \star 0$ $ -7 \star 0 = (-7)(0)+(2)(-7)-0$ $ \hphantom{-7 \star 0} = -14$.